The effects of class II elastic force on a dry skull measured by holographic interferometry.

A method was developed for measuring bone displacements due to orthodontic forces. By means of holographic interferometry, the effects of Class II elastics on a dry skull were investigated. The bone deformation induced by the elastic force was studied on double-exposed holograms and also by the live fringe method. The results of this study reveal that sutures in the skull behave as weak structures, creating an interruption in the fringe pattern. With regard to the nasofrontal suture, the main movement, as could be expected, was an anteroposterior displacement. Related to the first molar, chosen as the anchorage unit, the vertical displacement was most pronounced. Furthermore, according to the findings of this study, the zygomaticotemporal suture was behaving as a hinge axis in a transversal direction. The method developed seems to be suitable for measuring bone displacements qualitatively as well as quantitatively.